" In this experiment the heat at the dia phragm was diminished 18°, in the pelvis 21°.
" This greater diminution of heat in the second than in the first, we may suppose pro portional to the decreased power of the animal, arising from want of food.' * But extreme cold alone, by a painful effect induced on the sentient nerves, rouses the hibernating animal from its lethargy, as has been remarked already, and is illustrated by the following experiments of Hunter. " Having brought a healthy dormouse, which had been asleep from the coldness of the atmosphere, into a room in which there was a fire, (the atmosphere at 64°,) I introduced the thermo meter into its belly, nearly at the middle, be tween the thorax and pubis, and the quicksilver rose to 74° or 75°; turning the bulb towards the diaphragm, it rose to 80° ; and when I ap plied it to the liver, it rose to 81°.
" The mouse being placed in an atmosphere at 20°, and left there half an hour, when taken out was very lively, even much more so than when put in. Introducing the thermometer into the lower part of the belly, the quicksilver rose to 91°; and turning it up to the liver, to 93°.
" The animal being replaced in the cold atmosphere at for an hour, the thermome ter was again introduced into the belly ; at the liver it rose to 93°; in the pelvis to the mouse continuing very lively.
" It was again put back into an atmosphere cooled to 19°, and left there an hour; the ther mometer at the diaphragm was 87°; in the pelvis but the animal was now less lively.
" Having been put into its cage, the thermo meter being placed at the diaphragm, in two hours afterwards was at In these experiments the animals appear to have been roused partly by the state of the wound in the abdomen, but chiefly by the ex treme cold. They can scarcely, however, be considered as experiments upon hibernation, however interesting they may be in reference to reviviscenee from that state.
The fact of the fatal influence of excited re spiration during the augmented irritability of hibernation, contrasted with the similar fatal effect of suspended respiration, during the dimi nished irritability of the state of activity, will illustrate many of the causes, kinds, and phe nomena of death. Do not tlieEe resolve them
selves, in fact, into irritability insufficiently or excessively excited ? IV. Of torpor from cold.—It is highly im portant, and essential to the present investiga tion to distinguish that kind of torpor which may be produced by cold in any animal, from true hibernation, which is a property peculiar to a few species. The former is attended by a benumbed state of the sentient nerves, and a stiffened condition of the muscles ; it is the direct and immediate effect of cold, and even in the hibernating animal is of an injurious and fatal tendency; in the latter, the sensibility and motility are unimpaired, the phenomena are produced through the medium of sleep ; and the effect and object are the preservation of life.
Striking as these differences are, it is certain that the distinction has not always been made by former observers. In all the experiments which have been made, with artificial tempera tures especially, it is obvious that this distinc tion has been neglected.
True hibernation is induced by temperatures only moderately low. All hibernating animals avoid exposure to extreme cold. They seek some secure retreat, make themselves nests or burrows, or congregate in clusters, and, if the season prove unusually severe, or if their retreat be not well chosen and they be exposed in con sequence to excessive cold, many become be numbed, stiffen, and die.
In our experiments upon hibernation we should imitate nature's operations. Would any one imagine that the following detail contained the account of an experiment upon this sub ject ? " Le 3 t Jativier," says M. Saissy, " trois Ileums du soir, la temperature atmospliC rique Ctant A 1"•25 an-dessous de zero, cello d'un herisson engourdi profondement d au dessus, j'enfermai ce quadrupede dans un bocal de verre entoure de tuute part d'ime mix tion de glace et de muriate de soude. L'exces du froid le reveilla d'abord, mais trois heures out suffi pour le replonger dans one profonde torpeur.